Hi HN! I'm the developer of Telescopo, a universal file viewer for macOS.

I built this because I was tired of keeping different apps around for different file types. Preview for PDFs, Marked for Markdown, Xcode for code files, random apps for EPUBs. Telescopo handles 70+ formats in one native app.

Technical highlights:

- Metal acceleration for buttery smooth scrolling/zooming even with 1000-page PDFs - Syntax highlighting for 40+ languages with function detection - Renders Mermaid/PlantUML diagrams inline in markdown files - Real tabs and multi-window support (surprisingly rare in document viewers) - Instant loading - no progress bars, even for massive documents - 100% native Swift/AppKit, no Electron or web views

The interesting challenge was making disparate formats feel cohesive. A Python file, PDF, and EPUB need completely different rendering approaches, but the user should feel like they're using one consistent app.

Includes three themes - light, dark, and an animated cyberpunk mode (I know, but it's actually great for late night documentation reading).

Pricing: $4.99 one-time purchase, no subscriptions.

Would love feedback from the HN community. Already adding LaTeX support based on early feedback. What formats do you deal with that never seem to have good viewers?

Mac App Store: https://apps.apple.com/us/app/telescopo-universal-viewer/id6...

Happy to answer questions about the Metal implementation or building native Mac apps in 2025!